1. Field of the Invention
The present invention relates to a method for manufacturing a product by jetting droplets to an object to be coated.
2. Description of the Related Art
A droplet-jetting applicator is used not only in printing image information, but also in manufacturing steps for various flat panel displays: specifically, a liquid-crystal display, an organic EL (Electro Luminescence) display, an electron-emitter display, a plasma display, an electrophoretic display, and so forth.
The droplet-jetting applicator includes a droplet-jetting head (for example, an inkjet head) which jets droplets of a dispersion liquid such as ink, through multiple nozzles, to an object such as a substrate to be coated with the droplets. In this type of droplet-jetting applicator, the droplets from the droplet-jetting head are landed on the object to be coated therewith, and a predetermined coating pattern is formed to manufacture various products. Note that a dispersion liquid such as ink is filled through internal flow paths into multiple liquid chambers of the droplet-jetting head.
In general, a droplet-jetting-head filling device is used at an initial filling stage of filling the droplet-jetting head with a dispersion liquid (i.e., filling of empty internal flow paths and liquid chambers in the droplet-jetting head). At the initial filling stage, by utilizing a water-head difference, a pump or the like, this droplet-jetting-head filling device sends a dispersion liquid to the internal flow paths and liquid chambers thereof so slowly that the internal flow paths and liquid chambers can be filled without air bubbles remaining in the internal flow paths and liquid chambers. The flow rate at this stage is controlled so that, for example, a 10-cc dispersion liquid may be gradually filled into the internal flow paths and liquid chambers of the droplet-jetting head for approximately 30 minutes to 60 minutes.
The dispersion liquid used here includes multiple, for example, spacer particles and the like as a coating material. This dispersion liquid is formed by dispersing multiple particles in a dispersion medium. It should be noted that the spacer particles and the like are easily deposited in the medium, causing failure in jetting droplets by the droplet-jetting head. Against this problem, a printing method has been proposed to prevent the spacer particles from being deposited in the droplet-jetting head after the initial filling of a spacer dispersion liquid including the multiple spacer particles (see, for example, JP-A No. 2006-122814 (KOKAI)). In this printing method, a spacer dispersion liquid is either discharged from the droplet-jetting head, or supplied to and discharged from the droplet-jetting head, the droplet-jetting head is initially filled with the spacer dispersion liquid. Here, this event is performed depending on whether the already-filled droplet-jetting head is in a printing state or a waiting state.
Meanwhile, as described above, the dispersion liquid needs to be filled slowly so that the air bubbles can be prevented from remaining at the initial filling stage. Since the particles in the dispersion liquid are likely to be deposited during this filling stage, the multiple deposited particles may clog a nozzle of the droplet-jetting head, causing a failure in jetting droplets by the droplet-jetting head such as not jetting droplets.